Metallization layers are commonality utilized in semiconductor applications for electrically connecting one or more semiconductor devices, such as MOSFETs, IGBTs, diodes, etc. For example, a metallization layer may be used in an integrated circuit to electrically connect power and ground potential to individual transistor devices. Further, metallization layers may be used in an integrated circuit as interconnects for the input and output terminals of the transistors. A variety of processing techniques are available for forming semiconductor metallization layers such as electroplating, chemical or physical vapor deposition, etc. Lithography techniques are commonly utilized to provide metallization lines with precisely controlled width and pitch.
In many cases, copper is a preferred material for semiconductor metallization layers. Copper offers low electrical resistance and is therefore conducive to high frequency switching operation of semiconductor devices. Further, copper is advantageous in high power applications because it provides low resistive losses and high thermal conductivity. However, copper metallization lines may be susceptible to reliability issues. Particularly in the case of high-temperature and high-humidity conditions, copper is prone to corrosion, oxidation, and/or electromigration. Unless proper mitigation steps are taken, the risk of electrical short in copper metallization lines (e.g., between a source and drain line) due to copper dendrites and/or cathodic-anodic filamentation (CAF) may be unacceptably high.
Known techniques for mitigating the risk of electrical short in copper metallization lines include forming protective layers that seal the copper and prevent electromigration and/or diffusion of the copper. For example, protective layers formed from materials such as nickel (Ni), palladium (Pd) and gold (Au) may be used to protect and seal copper metallization layers. However, these techniques introduce undesirable expense and complexity to the process.